Couplings for flareless tubes, such as shown in U.S. Pat. No. 3,499,671, which include a deformable metal sleeve between a nut and body having threaded engagement with each other, have many uses in industry. This type of coupling is particularly convenient to use because the nut, body and sleeve can be preassembled to a finger-tight position wherein the sleeve remains undeformed and in which finger-tight condition the tube may be readily inserted through the nut and sleeve and into the body whereupon the installer need only tighten the nut upon the body to deform the sleeve into gripping and sealing engagement with the tube.
However, in some installations the fitting body, with the nut and sleeve in finger-tight position thereon, must be connected to a housing or panel prior to installation of the tube and in a vertical position in which the nut is lowermost. Now, when the tube is inserted it must be held in its proper position by the workman until the nut is tightened upon the coupling body for deforming the sleeve into tight gripping engagement with the tube. It is not always convenient for the workman to hold the tube during tightening of the nut in a manner to prevent the tube from slipping out of the coupling, either completely or partially.
In other cases, such as assembly line production of assembled tubes, the tube may be inserted into the loosely assembled coupling at one station and the nut tightened at another and the tube may partially withdraw during handling between the two stations.
In either case, the tube may not be in its proper position for final tightening of the nut with the result that the tube may not be securely gripped or sealed.